respect canonical flag in SubtreeIterator (#46)

* respect canonical flag in SubtreeIterator

* add more tests

Author: ranocha

src/RootedTrees.jl

@@ -512,8 +512,10 @@ end
 
   # find the next complete subtree
   subtree_last_index = _subtree_last_index(subtree_root_index, level_sequence)
-  subtree = RootedTree(view(level_sequence,
-                            subtree_root_index:subtree_last_index))
+  subtree = RootedTree(
+    view(level_sequence, subtree_root_index:subtree_last_index),
+    # if t is in canonical representation, its subtrees are, too
+    iscanonical(subtrees.t))
 
   return (subtree, subtree_last_index + 1)
 end

test/runtests.jl

@@ -246,6 +246,10 @@ end
   @test β(t17) == α(t17)*γ(t17)
   @test t17 == t1 ∘ t8
   @test butcher_representation(t17) == "[[[[τ]]]]"
+
+  # test non-canonical representation
+  level_sequence = [1, 2, 3, 2, 3, 4, 2, 3, 2, 3, 4, 5, 6, 2, 3, 4]
+  @test σ(rootedtree(level_sequence)) == σ(RootedTrees.RootedTree(level_sequence))
 end